   (let [prog-next (swap! prog-curr prog-frame-fn)
         ts (count @prog-history)]
     (swap! prog-history #(conj % [ts label prog-next]))
-    (swap! prog-ss #(assoc % ts (ago-snapshot ((:get-agw (first world))))))))
+    (swap! prog-ss #(assoc % ts (ago-snapshot (actx-agw world))))))
 
 ; -------------------------------------------------------------------
 

            [cbfg.world.lane]
            [cbfg.world.base :refer [world-cmd-loop]]))

(def prog-base    (atom {}))  ; Stable parts of prog, even during time-travel.
(def prog-curr    (atom {}))  ; The current prog-frame.
(def prog-hover   (atom nil)) ; A past prog-frame while hovering over prog-history.

  (when-let [ago-ss (get @prog-ss ts)]
    (reset! prog-curr prog-frame)
    (swap! prog-history #(vec (take (+ ts 1) %)))
    (ago-restore (actx-agw (:world @prog-base)) ago-ss)))

(defn on-prog-frame-focus [ts label prog-frame]
  (reset! prog-hover prog-frame)
